This invention relates in general to blown glassware such as drinking tumblers and stemware having a concave bottom surface. More specifically, it relates to crown bottom glassware of the type which requires a hollow parison having a thick or massive bottom section that is allowed to sag into a finish mold where it is blown into its final shape.
Normally such glassware is produced on automatic forming machines wherein the parison is rotated as it is allowed to sag into its respective paste mold and onto a crowned bottom plate in the mold.
A major problem in forming this type of glassware, particularly thick bottomed tumblers known as sham-bottomed tumblers, is that the heavy lower end of the parison frequently settles on the bottom plate slightly off-center. The crowned or convex surface of the bottom plate tends to worsen any off-center condition as does the rotation of the parison in the mold. As a result, there is an uneven distribution of glass in the bottom of the finished tumbler, and its internal bottom surface is lopsided. It is an object of this invention to provide a method and means for producing crowned bottom glassware with a symmetrical distribution of glass in the bottom region of the finished tumbler.